Electronic Circuit Function.
The electronic circuits of the boresight collimator are the lamp
circuit and the reticle heater control circuit.
In the reticle
heater control circuit, a reference voltage is supplied to the
differential amplifier and to the constant current source.
A
constant current from the constant current source is supplied to the
background temperature sensor and to the reticle temperature sensor,
which is located on the back of the reticle.
The output of the
reticle temperature sensor is applied through an amplitude control to
the comparator, where it is compared with the output of the
background temperature sensor.
The output from the comparator and
feedback from the heater driver control the differential amplifier.
The differential amplifier provides the input to the heater driver.
The output of the heater driver powers the IR source heater, which
raises the temperature differential between the source and the
reticle (target) to produce the IR pattern.
Figure 3-8.
Electronic Circuit Function.
58
MM4812
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